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  • 1
    Electronic Resource
    Electronic Resource
    Differentiation of Y79 cells induced by prolonged exposure to insulin (1997)
    Springer
    Molecular and cellular biochemistry 170 (1997), S. 163-170 
    Details
    ISSN: 1573-4919
    Keywords: human retinoblastoma ; Y79 cells ; differentiation ; insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Y79 human retinoblastoma cells are known to contain receptors for both insulin and insulin-like growth factors (IGFs), to produce these cytokines and release them in the culture medium. Previously we have demonstrated that IGFs and insulin stimulate Y79 cell proliferation through the involvement of type I IGF receptor and Insulin Receptor Substrate 1 (IRS-1). This paper studies the effect of prolonged exposure to insulin on Y79 cells. Cells grown for 10 days in the presence of insulin were reseeded and incubated once more with insulin. In the reseeded cells proliferation lowered and morphological changes appeared. After 10 days of reseeding, cells stopped proliferating and showed long ramifying neurite processes and varicosities consistent with neuronal differentiation. Morphological differentiation was accompanied by a marked increase in the content of total protein and in that of tubulin, the major protein constituent of microtubules, a marked increase in the content of specialized protein markers of dopaminergic and cholinergic differentiation (dopamine β-hydroxylase and choline acetyltransferase activities, respectively); a contemporaneous decrease in the content of glial fibrillary acidic protein (GFAP), a specific marker of glial cells, was also observed. Our results demonstrate that prolonged exposure to insulin induces Y79 cells to differentiate into a neuronal-like phenotype. At this moment it is not possible to establish the mechanism by which insulin induces this differentiative effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006813705101
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  • 2
    Electronic Resource
    Electronic Resource
    Induction of programmed cell death in human retinoblastoma Y79 cells by C2-ceramide (1998)
    Springer
    Molecular and cellular biochemistry 185 (1998), S. 7-15 
    Details
    ISSN: 1573-4919
    Keywords: human retinoblastoma cells ; apoptosis ; ceramide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract C2-ceramide, a cell-permeable analogue of ceramide, induced significant, dose- and time-dependent death in human retinoblastoma Y79 cells. Dying cells strongly displayed the morphology of apoptosis as characterized by microscopic evidence of cell shrinkage, membrane blebbing, nuclear and chromatin condensation and degeneration of the nucleus into membrane-bound apoptotic bodies. Upon induction of apoptosis Y79 cells evidence early phosphatidylserine externalization, as shown by annexin V-FITC. Apoptosis was also assessed by monitoring changes in cell granularity by staining with the combined fluorescent dyes acridine orange and ethidium bromide. C2-ceramide induced these morphological changes without a concomitant production of oligonucleosomal fragments responsible for the DNA ladder and without changes in p53 protein level. Apoptosis was accompanied by accumulation of a modified Bcl-2 protein with a slower-mobility form, and by proteolytic cleavage of PARP. The effect seemed to be specific for C2-ceramide, as C2-dihydroceramide, or other amphiphilic lipid analogues, or products of ceramide hydrolysis were ineffective. The effect also depended on mRNA and protein synthesis as it was markedly inhibited by actinomycin D and cycloheximide. Sphingomyelinase and interleukin-lβ, which are known to activate the sphingomyelin turnover leading to ceramide generation, also induced apoptosis mimicking the effects of ceramide. These findings propose ceramide as an activator of the suicidal program in Y79 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006836428202
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  • 3
    Electronic Resource
    Electronic Resource
    Insulin synthesis in chick embryo retinas during development (1994)
    Springer
    Neurochemical research 19 (1994), S. 821-825 
    Details
    ISSN: 1573-6903
    Keywords: Insulin ; chick embryo ; retina ; development ; HPLC analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Retinas of chick embryos contain insulin (1) and further, are capable of synthesizing it, as demonstrated by incubating retinas at different ages (7th–18th day) with [3H]leucine. The synthesized radioactive insulin was isolated and assayed by means of a HPLC procedure. The synthesis of insulin was found to be highest in the youngest retinas studied (day 7), afterwards it declined with age except for an increment found at 14–15 day. Explants of chick embryo retinas, cultured in vitro, rapidly degraded insulin. Nevertheless, the content of immunoreactive insulin in retinal explants diminished slowly with the age of culture, so that, after 8 days of incubation, it was about 60% of the content found in the retinas at the beginning of incubation. This was proof that cultured explants are capable of efficiently synthesizing insulin. The synthesized [3H]insulin was released from explants into the medium. This was evident also after 6–8 days in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00967450
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  • 4
    Electronic Resource
    Electronic Resource
    Chick embryo retina development in vitro: The effect of insulin (1995)
    Springer
    Neurochemical research 20 (1995), S. 803-813 
    Details
    ISSN: 1573-6903
    Keywords: Insulin ; chick embryo ; retina ; in vitro development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this paper we study the development of chick embryo retina culturedin vitro and the effects exerted by insulin. Retinas were removed from 7-day embryos and cultured in serum-and hormone-free medium for 7 additional days. Under these conditions retinal cells survived and underwent cholinergic differentiation, as previously ascertained by Hausman et al. (Dev. Brain Res., 1991, 59: 31–37). However, a great retardation of development was noted compared to uncultured control, 14-day retina. In fact both wet weight and DNA and protein content increased much slower than in ovo and the tubulin content decreased below even the starting value. In addition, although after 7 days in culture retinal cells were organized in identifiable layers, nevertheless the typical organization equivalent to 14-day in ovo retina was absent. The addition of insulin in the medium markedly increased the wet weight of cultured retinas, their protein content and the level of tubulin pools, particularly that of non-assembled fraction. Nevertheless insulin did not modify DNA synthesis and did not induce the increment of both neuron specific enolase and actin. Morphological observations show that insulin markedly increased the number and the thickening of the fiber layers. These results, together with the facts that retina synthesizes and secretes insulin and possesses specific insulin receptors suggest that insulin can have autocrine or paracrine regulatory functions in retinal development by exerting a general effect on retinal growth and a more specific one on tubulin production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00969692
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    Paper (German National Licenses)
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